Nonetheless, it is useful to discuss these to identify points on which they remain appropriate, and points on which they are clearly obsolete. To facilitate cross-referencing I shall discuss items in the same order as they appear in the IUBMB recommendations. Although
the 1981 recommendations are still applicable, in the sense that there has been no formal revision, I shall refer to them in the past tense in this chapter to it make easier to distinguish what was recommended then and what the members of STRENDA think now (Tipton et al., 2014). This introduction is deferred until after the discussion of kinetics. This section contained definitions of standard terms used in biochemistry, most notably BKM120 ic50 catalyst, concentration, enzyme, substrate, inhibitor, activator, effector IDH tumor and modifier. Most of these require
no comment, as they were defined in accordance with ordinary practice in biochemistry, but concentration was considered to be an abbreviation for amount-of-substance concentration, a term that most biochemists will never have encountered, and which is virtually never used by them as it is normally the only kind of concentration they ever use. Its formal SI unit is mol dm−3, but this is virtually never written in this way in biochemical publications, being (equivalently) written as mol l−l, mol L−1 or simply M. Although not stated in the recommendations it is generally accepted that any of these last three units can be prefixed m (milli, 10−3), µ (micro, 10−6), p (pico, 10−9), n (nano, 10−12), as appropriate. The rate of consumption Nitroxoline of a reactant of concentration [A] was defined
as equation(1) vA=−d[A]dtin which t represents time. Square brackets could be used without definition, as here, to represent concentrations. Other symbols, such as a for the concentration of A, were permissible, but needed to be explicitly defined. The rate of formation of a product 4 of concentration [P] is defined as equation(2) vP=d[P]dtThe terms rate and velocity are synonymous, and these are normally measured in M s−1, or one of the obvious variants implicit in the discussion above. Because of the minus sign in Eq. (1) the values of vAvA and vPvP are equal if A and P have equal stoichiometric coefficients, as is the case in most (but not all) enzyme-catalysed reactions, and if so the subscripts can be omitted from v and the term rate of reaction used. The section began by discussing the complications that arise when the stoichiometry is not one-to-one, when, for example, two molecules of the same product are generated when one molecule of substrate is consumed. Reactions of this kind are not common in enzyme kinetics, but they do occur, for example, the hydrolysis of maltose catalysed by α-glucosidase.